1. Field of the Invention
This invention relates to a paint containing a vinyl resin, and a method of manufacturing the same.
2. Description of the Prior Art
A vinyl resin containing a silyl group having a hydrolyzable group at its terminal or in its side chain, has many outstanding advantages. The hydrolyzable silyl group improves adhesion of the resin to an inorganic material. Moreover, it accomplishes cross-linking at room temperature, with the aid of water, particularly in ambient air, and forms a dense network structure which provides the resin with an outstanding degree of solvent resistance, water resistance, heat resistance, hardness, surface luster and weather resistance. All of these advantages have been priorly disclosed, for example in Japanese Patent Application Laid-Open No. 36395/79.
Such a vinyl resin has, however, been still unsatisfactory in a number of other respects. For example, although it is highly adhesive to an inorganic material, as in the case wherein a silane coupling agent is used, it does not show any satisfactory adhesion to an organic material. Also, the synthesis of a vinyl resin containing a silyl group tends to lack stability or reliability, since it is likely to increase in viscosity or form a gel during its synthesis.
In order to obtain such a vinyl resin having improved physical properties, it has been proposed to copolymerize an organic acid, such as acrylic or methacrylic acid. The use of an organic acid has, however, been found to give rise to a serious problem in the synthesis of such a resin. A silyl group containing vinyl resin may be synthesized by either of the following methods, for example:
(A) reaction between a vinyl resin having a carbon-carbon double bond and a hydrosilane, and
(B) copolymerization between a vinyl compound and a silyl compound having a polymerizable double bond.
If an organic acid, such as acrylic acid, is used for copolymerization, there is likely to result, a high degree of increase in viscosity and gelation. This tendency increases with increase in the number of hydrolyzable groups bonded to silicon. This is apparently due to the high acidity of an organic acid, and thus, its heavy catalytic action for the reactions in above methods (A) and (B).
Moreover, a silyl group containing compound lacks storage stability. Due to the reactivity of its silyl group, a silyl group containing compound is used for a wide range of applications, including the preparation of paints, coating agents, silane coupling agents and adhesives. Such a compound is, however, likely to increase in its viscosity and ultimately form a gel, as a result of the reaction of its silyl group during storage. In order to improve the storage stability of such a compound, the inventors have found it considerably effective to incorporate an alcohol and hydrolyzable ester compound, such as disclosed in Japanese patent application laid-open Nos. 25728/79 and 121181/79. The problem of storage stability is particularly serious when a silyl group containing vinyl resin is used for a paint containing a large quantity of a pigment, such as titanium dioxide. The moisture which the pigment contains seriously affects the storage stability of the paint, and is likely to cause an increase in its viscosity and its gelation.
The silyl group of a silyl group containing vinyl resin is represented by the formula: ##STR1## wherein X represents a hydrolyzable group, (R.sub.1) and (R.sub.2) each represents a hydrogen atom, or an alkyl, aryl or aralkyl group having 1 to 10 carbon atoms, and n is 1, 2, or 3. It differs in various respects from a silicon modified vinyl resin obtained by for example, the condensation of a compound of the formula: ##STR2## wherein m represents an integer, and a compound having a group represented as ##STR3## and represented by the formula: ##STR4## A silyl group containing vinyl resin is curable at room temperature, or at a temperature which is not higher than 80.degree. C., while a silicon-modified vinyl resin must be heated to a temperature of at least 100.degree. C. for curing. The --Si--C-- linkage produced by curing of the former resin is far more stable that the --Si--O--C-- linkage produced by curing of the latter resin, against not only acid, but also against water and alkali. Thus, the former resin also has an improved degree of water alkali resistance.